The present invention relates to an electronic circuit with one particular application of such an electronic circuit being as a circuit for driving a pixel of an organic electroluminescent device.
An organic electroluminescent (OEL) element can include a light emitting material layer sandwiched between an anode layer and a cathode layer. Electrically, this element operates like a diode. Optically, it emits light when forward biased, and the intensity of the emission increases with the forward bias current. It is possible to construct a display panel with a matrix of OEL elements fabricated on a transparent substrate and with at least one of the transparent electrode layers, one can also integrate the driving circuit on the same panel by using low temperature polysilicon thin film transistor (TFT) technology.
In a basic analog driving scheme for an active matrix OEL display, a minimum of two transistors are required per pixel (FIG. 1). T1 is for addressing the pixel and T2 is for converting the data voltage signal, to a driver current for an OELD to emit light at a designated brightness. This data signal is stored by the storage capacitor, Cstorage, when the pixel is not addressed. Although p-channel TFTs are shown in the figures, the same principle can also be applied for a circuit with n-channel TFTs.